The present invention relates to a magnetic core element suitable for use in a thin-film antenna and a thin-film antenna made of the magnetic core element. The present invention further relates to a card equipped with the thin-film antenna such as IC card type interface for transmitting signal to or receiving signal from computers, a seasonal traffic ticket used in automatic ticket inspecting system, etc.
Recently, PC cards which have functions of peripheral devices for personal computers such as external storage devices, modems, etc. have come to be used. For example, PC cards having IC card type interface meeting the standards of PCMCIA (Personal Computer Memory Card International) and. JEIDA (Japan Electronic Industry Development Association) have come to be employed in small terminal devices including notebook-type personal computers. The PC cards are classified into three types, type 1, type 2 and type 3, depending upon their sizes. The type 1 is the thinnest of the three types. Therefore, thinner elements have been required for producing such thin PC cards.
The PC card is connected to a personal computer, etc., mainly via a socket having electroconductive terminals. However, this connecting manner involves several drawbacks such as insufficient contact between terminals, insufficient protection against copying the informations stored in cards.
On the other hand, a connecting manner of an IC card interface and a computer by means of electromagnetic wave is free from insufficient contact and has advantage that remote transmission and/or remote receipt of signal may be possible.
The IC cards utilizing electromagnetic wave in transmitting and/or receiving signals may be applied to seasonal bus or railroad tickets, ski lift tickets, membership cards, identification (I.D.) cards, etc. By using such IC cards, the inspection or examination made by a person can be automated. For example, the IC card can be used in an automatic ticket examination system where an automatic ticket examining machine at a wicket or entrance receives from an IC card electromagnetic waves corresponding to the information recorded in the IC card, checks the information, and then, opens the gate when no problem is detected or closes the gate or alarms when a problem is detected. Such IC cards, like the PC cards, are required to be capable of being put into a pocket or wallet, for example, to be as thinner as credit cards. The IC cards may be further provided a message displaying function such as that of a paging receiver. In this case, the IC card may be receive-only.
Such thin IC cards which transmit and receive signals via electromagnetic waves should be provided with antenna which is thin and of high performance. The frequency range of the electromagnetic wave for the IC cards is limited within the range around 134 kHz by governmental regulations.
Conventionally, as the antenna for use in a card, those having ferrite cores have been employed. However, since the ferrite core is so brittle to easily cause cracks due to a slight deformation of a card, the card having the antenna of ferrite core is not suitable for carrying it in a trouser pocket, etc. To solve this problem, a card may be made resistant to deformation. However, production of a rigid or stiff card results in increased production cost and a large size of a card as well as an unpleasant feeling when carrying it in a trouser pocket, etc. due to its resistance to deformation or bending.
JP-A-5-267922 discloses an automobile antenna as an example of antennas having a core comprising a laminate of amorphous alloy thin strips. An antenna of amorphous alloy core can gain a high inductance because of a high magnetic permeability of the amorphous alloy, and is superior to an antenna of ferrite core because amorphous alloys have a Q-value (quality factor) higher than ferrites in the frequency range of 10-20 kHz. The Q-value herein used is represented by Q=.omega.L/R wherein .omega.=2.pi.f, L is inductance, and R is resistance including a coil loss.
JP-A-5-267922 teaches that the antenna of amorphous core disclosed therein is produced through heat-treatment at 390.degree.-420.degree. C. for 0.5-2 hours and that the thickness of antenna is preferred to be about 15-35 .mu.m. However, the antenna made from the amorphous core subjected to such heat-treatment as described above cannot gain a sufficient Q-value in a higher frequency range, i.e., a frequency range around 134 kHz at which IC cards is used.